Paint stripping composition

ABSTRACT

Inexpensive paint stripper compositions containing neither chlorinated nor alkaline solvents and well adapted for removing paints such as glycerophtalic, alkyd-urethane or acrylic urethane paints on a variety of substrates, e.g. wood and metal substrates comprise (a) 1 to 99% by volume of an aprotic polar solvent chosen from the group comprising: dimethyl sulfoxide, dimethyl formamide, N-methylpyrrolidone, N-methylmorpholine, γ-butyrolactone, acetonitrile and mixtures thereof; and (b) 99 to 1% by volume of an ether selected from the family of ethers having a flash point higher than 0° C. a molar volume less than 160 and a molecule that includes one or several methoxy groups.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a novel paint stripping compositionand, more especially, to a novel paint stripping composition containingneither chlorinated nor alkaline solvents. It also relates to theprocess for removing paint from a substrate, using this composition.

2. Description of the Prior Art

U.S. Pat. No. 3,600,322 describes the use of mixtures of methylenechloride and methanol fcr stripping paint, varnish or lacquers. Paintstripping compositions containing lactams or lactones, particularlyN-nethyl-2-pyrrolidone or butyrolactone, in admixture with other activecompounds, for example alkylene glycol ethers, are also known to thisart. Compare in this respect WO 86/03,766 and Wo 88/06,640 and U.S. Pat.Nos. 5,011,121 and 5,015,410.

U.S. Pat. No. 2,694,658 describes the use of DMSO as a solvent for paintstripping applications.

Nonetheless, all of the above solvents present the disadvantages ofbeing expensive and of being present in the compositions in considerableamounts. Thus, a serious need exists in the surface coating removalindustry for stripping formulations that are as effective as those ofthe prior art, but which are significantly less expensive.

SUMMARY OF THE INVENTION

Accordingly, a major object of the present invention is the provision ofimproved paint stripping compositions which avoid or conspicuouslyameliorate the above disadvantages and drawbacks to date characterisingthe state of this art.

Briefly, the present invention features a novel paint strippingcomposition comprising, by volume

(a) 1 to 99% of an aprotic( polar solvent chosen from the groupcomprising: dimethylsulfoxide (DMSO), dimethyl-formamide (DMF),N-methyl-pyrrolidone (NMP), N-methylmorpholine (NMm), γ-butyrolactone(BLo), acetonitrile (AcN) and mixtures thereof; and

(b) 99 to 1% of an ether selected from the family of ethers having :

a flash point higher than 0° C.

a molar volume less than 160,

a molecule having one or several methoxy groups.

The expression molar volume as used herein should be taken to mean theratio between molar mass and density.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

More particularly according to the present invention, in a preferredembodiment thereof the aprotic polar solvent of said paint strippingcomposition is dimethyl sulfoxide. According to another preferredembodiment, the said ether is selected from the family of ethers having:

a flash point higher than 0°C.

a molar volume less than 160,

a molecule having one or several methoxy groups

a molecule devoid of hydroxy groups.

In one preferred embodiment, the aprotic polar solvent and ether arepresent in amounts of, respectively, 1 to 20% and 99 to 80% by volume,and more preferably in respective amounts of 5 to 15% and 95 to 85% byvolume. A volume ratio of the components of about 10/90 is particularlypreferred.

In another preferred embodiment, the aprotic polar solvent and the etherare present in amounts of, respectively, 20 to 80% and 80 to 20% byvolume. In this embodiment, the aprotic polar solvent and the ether areparticularly advantageously present in amounts of, respectively, 40 to60% and 60 to 40% by volume, a volume ratio of 50/50 being speciallypreferred.

In one preferred embodiment of the paint stripping composition the etheris chosen from the group comprising: anisole, 1,2-dimethoxybenzene,1,3-dimethoxybenzene, 1,4-dimethoxybenzene, 1,2,3-trimethoxybenzene,2-methoxy-1,3-dioxolane, 2-methoxy-3,4-dihydropyrane,2,5-dimethoxytetra-hydrofurane, ethylene glycol dimethyl ether,diethylene glycol dimethyl ether, 1-ter-butoxy-2-methoxyethane. Thepreferred aprotic polar solvent is dimethyl sulfoxide.

The composition may include a surfactant, which is advantageously ahalogenated surfactant. Any known anionic, cationic or amphotericsurfactant is appropriate, a fluorinated surfactant, in other words onewhich includes one or several fluorine atoms being preferred, and asurfactant comprising the compound of formula:

    C.sub.6 F.sub.13 (OCH.sub.2 CH.sub.2).sub.n H, with n=10

being particularly preferred Such a compound is for example availablecommercially under the registered trademark Forafac® 1110.

The invention also provides a paint stripping composition for thestripping of acrylic-polyurethane or polyester-polyurethane paint on ametal substrate.

Additionally, the invention provides a paint stripping composition forstripping glycero-phtalic or alkyd urethane paint on a wood substrate.

The paint stripping composition according to the invention may alsoinclude conventional additives; such additives include one or more of: aco-solvent, an activator, a fire-proofing agent, a thickener, astabilizer, a surfactant, an evaporation inhibitor and, in general, anyadditive provided that said additive is not a chlorine-containingsolvent. In particular, addition of fats of animal or vegetable origin,for example certain esterified cuts, enables the flammability of themixture to be reduced. Cellulosic derivatives such as methyl celluloseor aerosils (such as pyrogenous silica) can be added to thicken themixture of solvents.

Addition of a surfactant enables stripping to be speeded up. Similarly,stripping is speeded up by the addition of an appropriate amount ofmethanol.

The invention also features a technique for removing paints and coatingfrom substrates by contacting such paints or coatings with thecompositions described above. Preferably, the paints are those typicallyused in the construction industry and the substrate is metal such asaluminum, or is wood.

The composition of this invention can be prepared by simply mixing thevarious constituents, using a stirrer or any suitable equipment.

The stripping process is carried out by contacting the object or surfacethat is to be stripped with a composition according to the presentinvention. Such contacting is continued until the paint swells, formsblisters and becomes detached. The substrates or surface to be strippedcan be contacted with a composition according to the present inventionin a variety of ways. Exemplary thereof are immersion, squirting,soaking using a paint brush, etc. The contacting is carried out at atemperature ranging from 5° to 40° C.; advantageously the ambienttemperature is generally comprised between 5° and 25° C. The contacttimes typically ranges from 15 to 45 minutes.

In order to further illustrate the present invention and the advantagesthereof, the following specific examples are given, it being understoodthat same are intended only as illustrative and in nowise limitative.

EXAMPLES

Technique employed

The substrates coated with paint were immersed in 30 ml of strippingcomposition according to the invention at ambient temperature (20°) forat least 30 minutes. Performance was estimated by inspecting the effectsobtained.

(A) Glycerophthalic paint+undercoat/wood

This was a mature paint which, hence, was perfectly cross linked. Whenthat which is herein defined as a "low-performance (o) solventcomposition" was used, the glycerophthalic paint (brilliant layer)remained intact or, at most, when inspected by binoculars (magnificationG=7×) several small bubbles spread over the surfaces could be detected.A "high-performance solvent composition (*)" produced a surface repletewith large scales. The substrate was then rinsed with a water jet(mechanical action) in order to eliminate the scales which were notadhered thereto. The surface was then inspected using binoculars (G=7×).When using a "very high-performance solvent combination (**)", it wasfound that the undercoat layer was partially detached over the entiretyof the surface.

(B) Alkyd-urethane paint/wood

As above, this was also a well matured paint and hence perfectly crosslinked. A low-performance solvent composition produced no observableeffect at the surface and the paint retained its brilliant finish. For ahigh-performance solvent composition (*), the surface was covered withscales, but these could not be detached even after intensive washingwith water. Contrariwise, after immersion in a very high-performancesolvent composition (**) it was observed that a simple water jetpermitted essentially all of the scales formed to be removed.

(C) Acrylic-polyurethane/aluminium paint

Using a low-performance solvent composition, only a beginning ofstripping was observed, around the edges of a board. After one hour,there was no improvement in stripping. A very high-performance solventcomposition (**) provided detachment of the entire film in less than 15minutes. Using only a high-performance composition (*), several extraminutes of immersion were required in order to elicit the same effect.In this case, the film was always detached in less than 30 minutes.Whether using high-performance or very high-performance compositions, anelongation of the film by several millimeters was always observed(relative elongation <30%).

(D) Epoxy/aluminium paint

After immersion for 1 hour, a softening of this very resistant paint wasobserved using high-performance compositions (*). Simple scraping wasthen sufficient to remove it with relative ease. A very high-performancesolvent stripping composition (**) based on formic acid, via itsmechanism or chemical action, did completely remove the epoxy layerwithout any scraping being required.

Results of tests

Eleven ethers were tested singly and in combination with DMSO and NMD,in a volume ratio of about 10/90.

Below, the results obtained for the eleven ethers alone or incomposition form according to the present invention are given andcompared with the action of a composition containingmethyl-tertio-butyl-ether, representative of the prior art.

These were the effects observed for the four types of paints associatedwith their supports for the cases listed A to D:

when the ethers were employed alone, practically no stripping action wasobserved;

when the ethers were associated with 10% DMSO or 10% NMP, it was noticedthat a swelling and detachment of the paint film was obtained over atleast 30% of the surface thereof, thus providing effective stripping.

The results obtained using the combinations of paints and supportslisted above under A to D in given in the table below:

    ______________________________________                                                              90% E +  90% E +                                                                              50% E +                                                100%   10%      10%    50%                                     Ether (E)      E      DMSO     NMP    DMSO                                    ______________________________________                                        anisole        0      **       **     **                                                                            (a) (b)                                 1,2-dimethoxybenzene                                                                         0      **       **     --                                      1,3-dimethoxybenzene                                                                         0      **       **     --                                      1,4-dimethoxybenzene                                                                         0      **       **     --                                      1,2,3-trimethoxybenzene                                                                      0      **       **     --                                      2-methoxy-1,3- 0      **       **     --                                      dioxolane                                                                     2-methoxy-3,4- 0      **       **     --                                      dihydropyrane                                                                 2,5-dimethoxytetra-                                                                          0      **       **     --                                      hydrofurane                                                                   ethyleneglycol 0      **       **     --                                      dimethylether                                                                 diethyleneglycol                                                                             0      **       **     --                                      dimethylether                                                                 1-tert.butoxy-2-                                                                             0      **       **     --                                      methoxyethane                                                                 methyl tertiobutylether                                                                      0      * to **  --     --                                      ______________________________________                                         (a) tests carried out on glycerophtalic and alkydurethane paints              (b) a slight improvement was noted with respect to the 90% E/10% DMSO         mixture.                                                                      (--) test not implemented                                                

The ethers employed in the invention are less flammable than thoseemployed to date for this purpose.

Use of the compositions according to the invention enables the bestperformance, as regards effectiveness of stripping and absence offlammability, to be achieved at least cost.

What is claimed is:
 1. A paint stripping composition comprising, byvolume:(a) 1to 20% of an aprotic polar solvent selected from the groupconsisting of: dimethyl sulfoxide (DMSO), dimethyl formamide (DMF),N-methylpyrrolidone (NMP), N-methyl-morpholine (NMm), γ-butyrolactone(BLo), acetonitrile (AcN) and mixtures thereof; and (b) 99 to 80% of anether, said ether having:a flash point higher than 0° C. a molar volumeless than 160, a molecule having one or several methoxy groups, and amolecule devoid of hydroxy groups, in which the ether is anisole,1,2-dimethoxybenzene, 1,3-dimethoxybenzene, 1,4-dimethoxybenzene,1,2,3-trimethoxybenzene, 2-methoxy-1,3-dioxolane,2-methoxy-3,4-dihydropyrane, 2,5-dimethoxytetrahydrofurane, ethyleneglycol dimethyl ether, diethylene glycol dimethyl ether, or1-tert-butoxy-2-methoxy ethane.
 2. The paint stripping compositionaccording to claim 1, wherein the ether is anisole.
 3. The paintstripping composition according to claim 1, wherein the ether is1,2-dimethoxybenzene, 1,3-dimethoxybenzene, 1,4-dimethoxybenzene or1,2,3-trimethoxybenzene.
 4. The paint stripping composition according toclaim 1, wherein the ether is 2-methoxy-1,3-dioxolane or2-methoxy-3,4-dihydropyrane.
 5. The paint stripping compositionaccording to claim 1, wherein the ether is2,5-dimethoxytetrahydrofurane.
 6. The paint stripping compositionaccording to claim 1, wherein the ether is ethylene glycol dimethylether or diethylene glycol dimethyl ether.
 7. The paint strippingcomposition according to claim 1, wherein the ether is1-tert-butoxy-2-methoxy ethane.
 8. The paint stripping compositionaccording to claim 1, in which said aprotic polar solvent is dimethylsulfoxide.
 9. The paint stripping composition according to claim 1 inwhich said aprotic polar solvent and said ether are present inrespective amounts of 5to 15% and 95to 85% by volume.
 10. The paintstripping composition according to claim 1, in which the volume ratio ofthe components is about 10/90.
 11. The paint stripping compositionaccording to claim 1, wherein the composition includes at least oneconventional additive that is a co-solvent, an activator, afire-proofing agent, a thickener, a stabilizer, a surfactant, anevaporation inhibitor, or any additive that is not a chlorine-containingsolvent.
 12. The paint stripping composition according to claim 1,further including a fluorinated surfactant comprising the compound offormula

    C.sub.6 F.sub.13 (OCH.sub.2 CH.sub.2).sub.n H, with n=10.


13. A paint stripping composition according to claim 1, for thestripping of acrylic-polyurethane or polyester-polyurethane paint on ametal substrate.
 14. A paint stripping composition according to claim 1,for stripping glycerophtalic or alkyd urethane paint on a woodsubstrate.
 15. A process for preparing compositions according to claim1, comprising mixing of the various components thereof using a stirreror any other appropriate equipment.